Radiating tube burner

ABSTRACT

A radiating tube burner in which the combustion air is introduced from the upper end of the unit through an inner feed pipe, then reversed into a concentric, parallel flow with the fuel gas which is introduced from the lower end. The burner head, carried by a stand pipe, produces a ring flame inside the space between the outer shell and the inner feed pipe.

United States Patent 1191 Burmeister Dec. 24, 1974 [5 RADIATING TUBE BURNER 3,081,818 3/1963 Bracomier et al. 431/353 x 3,174,474 3/1965 Jones et al. 126/91 A [75] Inventor' Karl'He'nz'Burme'ste" Kleve, 3,617,038 11/1971 Schmidt et al l26/9l A x Germany 73] Assignee: Ipsen Industries International,

Gesellschait mit beschrankter Primary Examiner-Edward G. Favors l-laftung, Kleve, Germany Attorney, Agent, or Firm-Joseph A. Geiger [22] Filed: Mar. 18, 1974 [21] Appl. No.: 452,283

' [57] ABSTRACT [30] Foreign Application Priority Data Mar. 17, 1973 Germany 2313421 A radiating tube burner in which the combustion air is introduced from the upper'end of the unit through an 52] us. c1. 126/91 A, 431/353 inner feedtpipe, then reversed into a Concentric, p r 511 Int. Cl. F23C 3/00 lel flow with t fuel gas which is introduced from the [58] Field of Search 126/91 R, 91 A, 360; lower -T burner head, Carried y a Stand P p 431/353 190 ;produces a ring flame inside the space between the outer shell and the inner feed pipe.

[56] References Cited UNITED STATES PATENTS 14 Claims, 4 Drawing Figures PATENTEUUEE24|974 3,855,993

SHEET 2 BF 2 Fig. 3

um H! yr" Fig.4 1

RADIATING TUBE BURNER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to encapsulated gas burners, and in particular to radiating tube burners in which an inner feed pipe is coaxially surrounded by an outer pipe or shell, enclosing within it a burner head to which combustion air and fuel gas is fed in a parallel flow. I

2. Description of the Prior Art Fromthe prior art in this field are known several versions of radiating tube burners in which the inner pipe is surrounded on both sides by flames, with the result that the longevity of these burners is considerably reduced.- Where this type of radiating tube burner is equipped with exhaust heat transfer means, or so-called recuperators, an additional disadvantage is encountered in the form of problems of burner replacement due to the heat distortion of the burner elements.

In oneparticular prior art solution, use is made of a gas-fueledcul-de-sac type radiating tube, the device consisting of a core pipe (fuel feed pipe), a perforated intermediate pipe (air feed pipe), and an outer pipe or shell (radiating shell), as well as a burner head arranged in the closed end portion of the outer shell (U.S. Pat. No. 3,187,740 and No. 3,220,401). This known gas-fueled radiating tube burner has several serious shortcomings. For example, the fuel burner unit, which a takes the form of a nozzle arranged at the end of the fuel feed pipe and air feed pipe, does not permit any substantial reduction in the air gap. No air is allowed to enter at the end face of the air feed pipe, with the result that cooling of the air feed pipe over its entire length, and especially near its end, is poor. Furthermore, this type of gas burner unit has only axially oriented bores for the supply of fuel gas, a fact which in practical applications leads to considerable depositsof soot on the air feed pipe. Lastly, these prior artdevices are not normally equipped with an exhaust heat recuperating means, so that their thermal efficiency is rather low.

A degree of improvement is achieved in another prior art gas-fueled cul-de-sac type radiating tube burner. This device features a similar burner head combined with one axially and several radially oriented bores for an axial and radial fuel feed flow, as well as an annular chamber arranged between the core pipe and the perforated intermediate pipe, air entering the closed end of the outer shell through air supply bores (Germany ,Offenlegungsschrift (Published Application) No. 2,054,264). One disadvantage of this solution stems from the fact that the supply of fuel gas and comdrical baffle be added to the core pipe. Obviously, this additional element renders the device more complex and costlier, in addition to impairing the ease of assembly and maintenance.

SUMMARY OF THE INVENTION It is a primary objective of the present invention to improve upon the prior art in this field, by eliminating the undesirable 'pre-heating of the fuel gas and the resultant risk of coking and cracking of the latter, with the aim of attaining a high thermal efficiency, while reducing assembly problems and improving serviceability to a considerable extent. Further shortcomings of prior art devices, such as premature burnup and distortion of the inner pipe and of the recuperator due to nonuniform heat loads, are likewise to be eliminated at minimal design and production expense.

The present invention attains the above objectives by suggesting a radiating tube burner in which the fuel gas feed pipe and the combustion air feed pipe are connected to the device at oppositeends of the radiating tube shell, and where the combustion air conduit includes a flow reversing shell on the gas intake end. As a consequence, the flame is no longer confined within the inner pipe, but it burns in the annular space between the inner feed pipe and the outer shell. This inner feed pipe, which can therefore be considerably smaller in diameter, now supplies comparatively cold combustion air, with the result that the average temperature of the inner feed pipe is now considerably below temperatures encountered on inner pipes of known devices.

In a preferred embodiment of the invention all parts' are designed for easy assembly, by simply inserting them either from above or from below into the ,two open ends of the outer shell. This shell is preferably a 1 The preferred embodiment of the invention, as mentioned, has the combustion air intake passing through the inner feed pipe, the flow of fuel gas to the burner head passing througha concentric annular. space between an air flow reversing shell and the inner wall of an upwardly reaching stand pipe. This stand pipe also carries the burner head and the reversing shell. The combustion air which enters the burner unit from its upper end is thus reversed in its flowdirection to create a parallel flow with the fuel gas entering from the bottom end and flowing toward the burner head via the in- I termediate annular passage between the flowreversing shell and the stand pipe. The burner head and the flow.

' reversing shell may be conveniently combined as a single part. The burner head itself features a plurality of angled fuel gas entry passages. This embodiment is characterized by a very simple structure, offering ease of access for inspection and replacement of component parts, thereby greatly reducing maintenance costs.

The invention further suggests that the flow reversing shell be provided on its periphery with several radial passages through which a portion of the combustion air passes the parallel fuel gas flow so that it becomes admixed thereto, before reaching the burner head-This premixing feature improves the combustion of the fuel gas with the air. Anotherimportant feature of the invention concerns itself with the structure of the burner head itself which suggests two circular rows of angled fuel entry passages for mixing the fuel gas to the combustion air. One set of passages is oriented at a mixing angle of 45, a second set of entry passages having a shallow angle of 15. The relationship between these two series of gasentry passages determines the shape and the lengthof the flame produced by the burner.

Lastly, it' turns out that an additional advantage ob-, tained with this novel device .is a low level of noise generation, resulting from the various improvements outlined above. 1

A portion of the-exhaust heat can be utilized by adding to the'intake side of the inner feed pipe a recuperator section. For this purpose, it is suggested that the inner feed pipe be provided with surface-increasing elements in its length portion located at the level of the furnace insulation. These surface-increasing elements are preferably in the form of heat transfer pins pressed into the inner feed pipe in a double helix pattern of orientation along the axis of the inner feed pipe. Besides creating a large surface for heat transfer, these heat transfer pins also create turbulance in the passing exhaust gases so as'to intensify the heat transfer.

The burner unit may further include'a pilot burner for back ignition purposes arranged near the air intake end of the tube burner. The upper end of the burner may further include a compensator section permitting longitudinal adjustments under thermal expansion of the outer burner shell. 7

In summary, the suggestedstructure offers a possibility to avoid the risk of burnup of the inner feed pipe,

' is readily accessible for inspection and replacement of parts during maintenance. Lastly, this burner unit exhibits a high degree of thermal efficiency, because exwhich, when installed for operation inside a furnace,

extends transversely across the furnace from its upper wall 2 to its lower wall 3, to which the burner unit is sealingly mounted in a conventional manner. The inner sides of the furnace walls 2 and 3 carry wall linings 4 and 5, respectively.

The radiating tube burner unit 1 consists of a ceramic shell 6 whose length is such that it extends at least from the furnace wall 2 into the furance wall 3, but which, in the example illustrated in the drawing, extends a short distance above the upper furnace wall 2. The ceramic shell 6, which constitutes the outermost tube of the assembly, has excellent resistance characteristics under high temperatures and is therefore particularly suited for use as-a radiating tube. The two ends of the ceramic shell 6 are open for the insertion and mounting Y with dotted lines), a burner head 9 which, together with a flow reversing shell 10, forms a one-piece unit, and a stand pipe 12 with a mounting flange l1 positioning the burner head 9 in the lower portion of the burner unit 1. The inner feed pipe 7 supplies a continuous flow of combustion. air to the burner head 9, while fuel gas is supplied to head 9 through the stand pipe 12, The intake connectionsfor fuel gas .and for combustion air are thus located at opposite ends of the radiating tube burner. In the exploded representation of FIG. 1 is further shown a compensator section 13 surrounding and cessive'heating of the fuel gas with-the resulting coking and cracking phenomena are avoided, and because the exhaust heat recuperation through large-surface, turbulance creating elements is improved, and furthermore, because the burner head itself has a flame of conveniently adjustable shape and length which insures complete combustion and also permits a safe and gen- 'tle back ignition.

BRIEF DESCRIPTION OF THE DRAWING- Further special features and advantages of the invention' will become apparent from the description following below, when taken together with the accompanying drawings which illustrate, by way of example, an embodiment of the invention, represented in the various figures as follows:

FIG. 1 is an elevational view of a radiating tube burner unit embodying the invention, the various corn- DESCRIPTION OF Tl-IE PREFERRED EMBODIMENT In FIG. 1 of the drawing are shown the basic components of a radiatingtube burner assembly. The reference numeral 1 indicates the radiating tube burner unit upper furnace wall 2. Thelower end portion of the unit isretained by means .of a mounting ring 14 which, together with the mounting flange 11 of the stand pipe 12 is similarly bolted to the lolwer furnace wall 3. The

mounting flange 11 further includes a central inlet 15 for the supply of fuel gas to the inside of the stand pipe 12. Suitable sealing elements may be provided between the ceramic shell 6, the furnace walls, and the abovementioned mounting elements.

Prior to bolting ofthe stand pipe 12 to the lower furnace wall 3 by means of its mounting flange 11, the stand pipe 12 is attached to the burner head 9 and its flow reversing shell 10 which reaches deep into the stand pipe 12 in a concentric relationship. This subassembly can be conveniently inserted into the ceramic shell 6 through its lower open end which is accessible from the outside of the lower furnace wall 3'.

The inner feed pipe 7 is inserted into the ceramic shell6 from above, reaching concentrically through the furnace insulation 4. This recuperator section 8 consists of a series of heat transfer pins 18 extending transversely across the feed pipe 7, successive axially spaced pins being angularly offset along a double helix. This double helix arrangement causes the combusted exhaust gases to transfer a considerable amount of heat to the pins 18 which transmit this heat to the combustion air entering the burner through the air inlet 16.

FIGS. 3 and 4 of the drawing illustrate, at an enlarged scale, theburner head 9 and its integral flow reversing shell 10 and-the stand pipe 12 which carries the former. The burner head 9 forms a kind of collar on the upper end of the flow reversing shell 10, defining a downwardly facing axial recess 19 near the junction between head 9 and shell 10 which engages and centers the upper end of the stand pipe 12.

Inside the burner head 9 itself are arranged incircular outline two series of fuel passages 20 and 21 linking the axial recess 19 with an enlarged inner diameter portion of the head 9. The two series of fuel passages 20 and 21 are arranged at different angles to the burner axis for an optimal mixing and combustion of the fuel gas with the combustion air which flows upwardly in the annular passage between the inner feed pipe 7 and the burner head 9. Through experiments it was found that a suitable angle or orientation is 15 for the passages 20, and 45 for the passages 21. Obviously, the

specific relationship between .these two series of fuel passages determines the shape and the length of the combustion flame.

The flow reversing shell 10 has the general shape of a deep pot with a central passage 22 in its bottom portion and several radial passages 22' in its sidewall near the bottom end. Combustion air flowing through the passages22 and 22 joins the parallel flowing fuelgas stream, thereby'producing a pre-mixingof the combustion air' and fuel gas.

To the stand pipe 12 of the burner is integrally connected a mounting flange 11 with a central inlet 15 for the fuel gas. The flange 11 is appropriately offset on its upper side, in order to provide centering means for the mounting ring 14 f the ceramic shell 6, the flange l1 and the mounting ring 14 being bolted against the outer side of 'the lowerfurnace wall'3. The mounting flange 11 and the'stand pipe 12 are preferably joined by a cir cular weld, the upper end of the pipe .12 having a taper'ed face with which it engages the earlier-mentioned axial recess 19 of the burner head 9. It should be understood that the above structural suggestions relate to a vertical arrangement of the radiating tube burner unit 1. If it is desired to have a horizontal orientation of the unit, some minor modifications of these attachments and connections of the component parts may be necessar iii operation, the radiating tube burner of the invention is simultaneously supplied with combustion 'air through the air connection 16 at the top of the burner and with fuel gas through the gas inlet 15 at the bottom of the burner. unit 1. The combustion air flows through 1 the recuperator section 8 of the inner feed pipe 7,

whereby its temperature is raised through contact with the heat transfer pins 18. The pre-heated combustion air, after exiting from the bottom end of the inner feed burner head 9 in a parallel, concentric stream with the fuel gas. A portion of the combustion air leaves the flow reversing shell through the passages 22 and 22 and is pre-mixed with the fuel. gas flowing in the annular space between the stand pipe 12 and the shell 10.

The fuel gas enters the stand pipe 12 from below through inlet 15, moving upwardly inside the earliermentioned annular space between stand pipe 12 and shell 10, under pre-mixing with combustion air. The final mixing of air and fuel gas occurs in the burner head 9 where the fuel gas flows through the two series of angled fuel passages 20 and 21 into the annular parallel flow of combustion air. The arrangement suggested by the invention produces a stable flame from the combustion mixture of fuel gas and air, approximately as shown in FIG. f the drawing. The combustion exhaustgases move upwardly in the annular space between the ceramic shell 6 and inner feed pipe 7, past the recuperator section 8, after which they are lead away from the radiating tube burner in a known manner which is not further described here.

The radiating tube burner of the invention can be operated with coal-derived gas, natural gas, propane, butane, and other similar gaseous fuels. Depending on the particular fuel gas used, the degree of thermal efficiency of the burner is 70 percent and higher. Through flow reversing shell 10 which guides the combustion air upwardly in the annular space between the pipe 7 and the shell 10. The combustion air now flows to the experiments in which the combustion was shut off, followed by quick removal of the stand pipe and burner head, it was found that the lower end of the inner feed pipe 7 which reaches into the flow reversal shell 10 had remained dark. In its length portion extending between the furnace insulations 4 and 5, the inner feedpipe 7 reaches approximately the same temperature as the furnace itself, The recuperator section 8 is again dark in the upper portion of the furnace insulation 4. The burner head 9 also reaches approximately furnace temperature. The lower half of the stand pipe 12 remains dark during operation.

It should be understood, of course, that the foregoing disclosure describes only preferred embodiments of the invention and that it is intended to cover all changes and modifications of these examples of the invention which fallwithin the Scope of the appended claims.

I claim: f

1. A radiating tube burner assembly for the continu-v ous combustion of fuel gas with air, the burner assembly being mountable across spaced upper and lower walls of a furnace and comprising in combination:

an upright elongated tubular outer shell having an open upper end; I

a combustion air feed pipe of a much smaller diameter than said shell extending through the upper end thereof along the longitudinal axis of the shell and having an open lower end positioned a distance above the lower end of the shell;

a combustion air inlet connection on the upper end of said air feed pipe;

a burner head mounted inside said outer shell a distance above the lower end of said air feed and surrounding the latter in such a way as to define an air flow passage therebetween;

a flow reversing shell extending downwardly from leads upwardly from they open lower end of said pipe to said air flow passage inside the burner head;

a fuel gas inlet at the lower end of said outer shell;

a fuel gas flow channel surrounding the outside of said flow reversing shell and leading upwardly inside said'outer shell from the fuel gas inlet to the burner head; and

means for mixing the upwardly flowing combustion air and the surrounding likewise upwardly flowing fuel gas for combustion above the burner head in the space defined between said air feed pipe and said outer shell. 2. A burner assembly as defined in claim 1, wherein:

the lower end of said outer shell is likewise open;

the assembly further comprise s'a removable flange closing the lower shell end;

said flange includes means for supporting the burner head; and I said fuel gas inlet is provided as a part of said flange.

3. A burner assembly as defined in claim 2, wherein:

the outer shell includes a mounting ring at its lower end;

said flange is a mountingflange engaging the mount- .ing ring from below; and I I the assembly further comprises means for sealingly securing the mounting ring and mountingflange to the lower furnace wall.

4. A burner assembly as defined in claim 3, further comprising:

means for sealingly securing .the upper end of the outer shell to the upper furnace wall in such a way as to accommodate longitudinal expansion and contraction of the outer shell relative to the furnace walls,

5. A burner assembly as defined in claim 2, wherein:

the burner he'ad supporting means is a stand pipe whose lower end is connected to said flange, communicating with its fuel gas inlet, and whose upper end carries the burner head;

said stand pipe surrounds and encloses said flow reversing shell, thereby defining said fuel gas flow channel leading from the fuel gas inlet to the burner head; and the flange, stand pipe, and burner head are insertable into, and removable from the outer shell, through its lower end, as a sub-assembly. 6. A burner assembly as defined in claim 5, wherein:

' the flow reversing shell is integrally connected to the burner head and concentricallysurrounds the air feed pipe, thereby defining said air flow channel, and the air feed pipe in turn is concentrically surrounding by the stand pipe, thereby defining said 8' fuel gas surrounded channel; and the mixing means for the combustion air and fuel gas includes a plurality of fuel passages in the burner head linking the upper end portion of said fuel gas flow channel with said air flow passage inside the burner head. 7. A burner assembly as defined in claim 6, wherein:

said fuel passages in the burner head include a first series of converging fuel passages arranged on an inner circle and inclined at an angle of approximately 45 from the vertical direction, and a second series of converging fuel passages arranged on an outer circle and inclined at an angle of approximately 15 from the vertical direction.

8. A burner assembly as defined in claim 7, wherein:

said mixing means further includes pre-mixing passages in the wall of the flow reversing shell through which a portion of the combustion air flowing inside the air flow channel can pass into the fuel gas flow channel for pre-mixing with the fuel gas.

9. A burner assembly as defined in claim 1, wherein:

the combustion air feed pipe includes recuperator means in the upper portion of the space between it and the outer shell for the transfer of heat from the combustion exhaust gases flowing upwardly through said space to the combustion air flowing downwardly'inside said feed pipe.

10. A burner assembly as defined in claim 9, wherein:

12. A burner assembly as defined in claim 11,

wherein:

said heat transfer pins are pressed into the air feedpipe and oriented in a pattern of regular axial and angular spacing so as to give the appearance of a double helix on the outside of the air feed pipe.

13. A burner assembly as defined in claim 1, further comprising:

means for back igniting the combustion flame-from the upper end of the outer shell. 14. A burner assembly as defined in claim 1, wherein:

said outer shell is a tube of ceramic material. 

1. A radiating tube burner assembly for the continuous combustion of fuel gas with air, the burner assembly being mountable across spaced upper and lower walls of a furnace and comprising in combination: an upright elongated tubular outer shell having an open upper end; a combustion air feed pipe of a much smaller diameter than said shell extending through the upper end thereof along the longitudinal axis of the shell and having an open lower end positioned a distance above the lower end of the shell; a combustion air inlet connection on the upper end of said air feed pipe; a burner head mounted inside said outer shell a distance above the lower end of said air feed and surrounding the latter in such a way as to define an air flow passage therebetween; a flow reversing shell extending downwardly from said burner head and enclosing the portion of the air feed pipe which reaches below the burner head so as to define an air flow channel between said pipe and the inner wall of said shell, which channel leads upwardly from the open lower end of said pipe to said air flow passage inside the burner head; a fuel gas inlet at the lower end of said outer shell; a fuel gas flow channel surrounding the outside of said flow reversing shell and leading upwardly inside said outer shell from the fuel gas inlet to the burner head; and means for mixing the upwardly flowing combustion air and the surrounding likewise upwardly flowing fuel gas for combustion above the burner head in the space defined between said air feed pipe and said outer shell.
 2. A burner assembly as defined in claim 1, wherein: the lower end of said outer shell is likewise open; the assembly further comprises a removable flange closing the lower shell end; said flange includes means for supporting the burner head; and said fuel gas inlet is provided as a part of said flange.
 3. A burner assembly as defined in claim 2, wherein: the outer shell includes a mounting ring at its lower end; said flange is a mounting flange engaging the mounting ring from below; and the assembly further comprises means for sealingly securing the mounting ring and mounting flange to the lower furnace wall.
 4. A burner assembly as defined in claim 3, further comprising: means for sealingly securing the upper end of the outer shell to the upper furnace wall in such a way as to accommodate longitudinal expansion and contraction of the outer shell relative to the furnace walls.
 5. A burner assembly as defined in claim 2, wherein: the burner head supporting means is a stand pipe whose lower end is connected to said flange, communicating with its fuel gas inlet, and whose upper end carries the burner head; said stand pipe surrounds and encloses said flow reversing shell, thereby defining said fuel gas flow channel leading from the fuel gas inlet to the burner head; and the flange, stand pipe, and burner head are insertable into, and removable from the outer shell, through its lower end, as a sub-assembly.
 6. A burner assembly as defined in claim 5, wherein: the flow reversing shell is integrally connected to the burner head and concentrically surrounds the air feed pipe, thereby defining said air flow channel, and the air feed pipe in turn is concentrically surrounding by the stand pipe, thereby defining said fuel gas surrounded channel; and the mixing means for the combustion air and fuel gas includes a plurality of fuel passages in the burner head linking the upper end portion of sAid fuel gas flow channel with said air flow passage inside the burner head.
 7. A burner assembly as defined in claim 6, wherein: said fuel passages in the burner head include a first series of converging fuel passages arranged on an inner circle and inclined at an angle of approximately 45* from the vertical direction, and a second series of converging fuel passages arranged on an outer circle and inclined at an angle of approximately 15* from the vertical direction.
 8. A burner assembly as defined in claim 7, wherein: said mixing means further includes pre-mixing passages in the wall of the flow reversing shell through which a portion of the combustion air flowing inside the air flow channel can pass into the fuel gas flow channel for pre-mixing with the fuel gas.
 9. A burner assembly as defined in claim 1, wherein: the combustion air feed pipe includes recuperator means in the upper portion of the space between it and the outer shell for the transfer of heat from the combustion exhaust gases flowing upwardly through said space to the combustion air flowing downwardly inside said feed pipe.
 10. A burner assembly as defined in claim 9, wherein: said recuperator means is a recuperator section of the air feed pipe, located at approximately the level of the upper furnace wall; and the recuperator section includes a plurality of surface-increasing elements attached to the air feed pipe and projecting into the exhaust gas flow.
 11. A burner assembly as defined in claim 10, wherein: said surface-increasing elements are axially spaced heat transfer pins projecting diametrally across the inside of the air feed pipe and across said space between the pipe and the outer shell.
 12. A burner assembly as defined in claim 11, wherein: said heat transfer pins are pressed into the air feed pipe and oriented in a pattern of regular axial and angular spacing so as to give the appearance of a double helix on the outside of the air feed pipe.
 13. A burner assembly as defined in claim 1, further comprising: means for back igniting the combustion flame from the upper end of the outer shell.
 14. A burner assembly as defined in claim 1, wherein: said outer shell is a tube of ceramic material. 